Device for tensioning the thread on a textile machine

ABSTRACT

A device for tensioning the thread on a textile machine, which comprises a retaining pulley rotatable by a pulled thread, and a brake for braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley. The brake comprises control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine.

United States Patent Monney I Jan. 118, R972 [54] DEVICE FOR TENSIONING THE THREAD ON A TEXTILE MACHINE [72] Inventor: Michel Monney, Geneva, Switzerland [73] Assignee: Plasmeca, Jean Piemontesi & Cie,

Carouge, Switzerland [22] Filed: Apr. 6, 1970 [2l] Appl. No.: 25,686

[30] Foreign Application Priority Data Apr. 19, 1969 Switzerland ..6025/69 [52] US. Cl ..66/146 [51] ....D04b 15/44 [58] Field of Search ..66/132, 146

[56] References Cited UNITED STATES PATENTS 2,519,882 8/1950 Bullard et al ..66/146 X 2,912,185 ll/l959 Vossen .66/l46 X 3,263,454 8/1966 Butler ..66/132 Primary Examiner-Louis K. Rimrodt Attorney-Ernest G. Montague [57] ABSTRACT A device for tensioning the thread on a textile machine, which comprises a retaining pulley rotatable by a pulled thread, and a brake for braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley. The brake comprises control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine.

4 Claims, 1 Drawing Figure DEVlCE EOE TENSIONING THE THREAD N A TEXTILE MACHINE This invention relates to a method of and device for tensioning thread on a textile machine, more particularly on a knitting machine.

Devices which comprise a retaining pulley rotated by the pulled thread and a brake for braking the rotation of the pulley to give a specific preliminary tension to the thread downstream of the pulley, have been suggested which comprise an electrical induction brake (eddy current brake) permanently acting on the pulley. in this way, the preliminary tension of the thread is kept practically constant and this is a major disadvantage, particularly when an elastic or resilient thread is being worked on a knitting machine. In such cases, to obtain very elastic fabric zones, the preliminary tension imparted to the thread must be very high so that the brake must then exert a pronounced action on the pulley. On the other hand, during other stages of the production process, the thread must have much less tension or even be slack, particularly so that it may be held in a thread guide while it is being cut.

Although such devices are adjustable when the machine is stationary, they have no control means for adjusting the thread tension during specific stages of the process of working the thread on the machine.

An object of the invention is to provide an improved tensioning device.

According to the present invention, there is provided a device for tensioning the thread on a textile machine, which comprises a retaining pulley rotatable by a pulled thread, and a brake for braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley, the brake comprising control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine.

The invention also provides a method of tensioning the thread on a textile machine, which comprises rotating a retaining pulley with a pulled thread, and braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley, the brake comprising control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, the single FIGURE of which diagrammatically shows, partly in section, an embodiment of the invention.

Referring now to the drawings the device illustrated is intended for tensioning a thread T on a textile machine and comprises a retaining pulley l rotatable by the thread T bearing against a groove 2 of the pulley, the base of which is lined with rubber at 3.

The thread T coming from a bobbin (not shown) bears on the pulley 1 over an angle of approximately 90 before reaching a thread guide illustrated diagrammatically at 4, from which it is fed to a working station of the machine where, for example, it is knitted.

The pulley l is mounted on a shaft 6 borne by a support 7 fixed on a frame 8 of the machine. It cooperates with a brake described hereinafter, which brakes the rotation of the pulley 1 to give a predetermined tension to the thread in a part T1 (not shown) situated downstream of the pulley.

The brake comprises a mild steel plate 9 rigidly secured to the pulley l and a magnet 10 borne by the shaft 6. The magnet 10 comprises a core 11 of nonmagnetic material (for example a plastics material), accommodating six magnetic members 12 hearing against a steel ring 13 accommodated in a rear hollow of the core E1.

When the brake is engaged, the magnet 10 occupies the raised position shown in the right-hand part of the device as shown, and, in this position, there is just a small air gap 14 between the plate 9 and the end face of the magnetic members 112. When the plate rotates, eddy currents are induced in the plate 9 so that the magnet 10 exerts a braking action on the pulley 1, such action increasing as the airgap 14 decreases.

The magnet 10 is mounted slidably on the shaft 6 and a spring 15 disposed between a shoulder of the ring 13 and the end of a bush 16 screwed on the shaft 6 tends to hold it in the top position bearing against an abutment consisting of a resilient ring 17 disposed in a groove in the bush 16. The axial position of the bush 16 along the shaft 6 and thus the width of the minimum airgap 14 can be adjusted by rotating the bush 16 on the shaft 6. The bush 16 has a graduation 16a which moves with respect to a reference mark 19a provided on a fixed ring 19 screwed on the shaft 6. The support 7 is clamped between this fixed ring 19 and a nut 21 also screwed on the shaft 6.

The shaft 6 is fon'ned with an axial duct 22 containing a block 23 having two radial arms 24 passing through a diametric slot 25 in the shaft and the ends of which engage in two diametrically opposite notches 26 of the core 11 which is thus prevented from turning on the shaft 6.

The block 23 is secured to one of the ends of a cable 27 passing through the duct 22, the other end being attached, by an adjustable stop device shown at 28, to the end of an actuating lever 2'9.

The lever 29 pivoted at 30 on a support 31 rigidly secured to the machine frame 8 bears a roller 32 cooperating with a cam 33 provided on a control shaft 34. By means of mechanisms which are not shown, the shaft 34 also controls the progress of the stages in the process of working the thread as carried out by the machine.

When the roller 32 is situated opposite a low part 35 of the cam, the block 23 can occupy its top position shown in respect of its right-hand half so that the magnet 10 urged by the spring 15 is in its forward position determined by the adjustable stop 17 and exerts it maximum braking action.

The cam 33 rotating during operation of the machine in the direction of the arrow F, a raised part 36 of the cam is brought opposite the roller 32 during another stage of the working process so that the block 23 is lowered by means of the cable 27 into the bottom position shown in respect of its left-hand half. The magnet 10 is then withdrawn against the action of the spring 15 so that the airgap has the maximum value shown at 37, which is sufiicient for the action of the brake on the pulley to be practically zero, the pulley 1 then being loose on the shaft 6.

After this instantaneous disengagement of the brake, for a following phase of the process, the roller 32 cooperates with a part 38 of the cam at an intermediate level, the block 23 can then partially move upwards, the brake reoperating and initially exerting only a small opposing force on the pulley.

By appropriate design of the contour of the cam 33, it is thus possible to obtain automatically a periodic braking program for the pulley, which may contain maximum braking stages, nonbraking stages when the pulley is loose on it shaft, or moderate braking stages, depending upon the specific stages of the process of working the thread on the machine.

Complete disengagement of the pulley l, which may be obtained when the brake is inoperative, enables the pulley to turn freely even at high angular velocity.

Consequently, if this disengagement is carried out when the thread is cut, the pulley can continue to rotate rapidly even after the thread is stopped, in order instantaneously to eliminate any tension in the tread upstream of the thread guide. Thus, even a very resilient thread can be retained in a thread guide, although the thread previously has a very high tension during a preceding stage.

The control of the braking process to a given program enables the thread tension to be greatly increased, and this is very advantageous with very resilient or elastic threads. Firstly, more compact and stronger zones may then be obtained in fabrics, while secondly the consumption of resilient or elastic thread, which is generally expensive, may be vary substantially reduced.

The device hereinbefore described may readily be incorporated. in existing textile machines having a cam shaft. The connection between the brake and the cam may be of any type, more particularly by means of a sheathed cable, when a rigid or more direct control is impossible.

Apart from the control of the brake by the cam, manual rotation of the bush 16 provides an extensive adjustment of the maximum braking power.

Although braking by means of eddy currents has the advantage of avoiding any contact between the moving parts, in a variant of the device according to the invention, the brake could be of some other type, for example, electromagnetic or hydraulic with a friction lining.

What is claimed is:

1. A device for tensioning the thread on a textile machine, which comprises a retaining pulley rotatable by a pulled thread, and a brake for braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley, the brake comprising control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine, the control means are adapted to render the brake instantaneously inoperative, so that the retaining pulley is the loose on its shaft, an electrical induction brake formed by a magnet and a plate which are rotatable relatively to one another on rotation of the retaining pulley, the control means being adapted to move the magnet and the plate apart from one another in order to reduce the opposing force.

2. A device according to claim 1, wherein the plate is rigidly secured to the retaining pulley and the magnet disposed opposite the plate is mounted movably on a support.

3. A device according to claim 2, wherein the support comprises a stop against which the magnet may bear in the advanced position, and resilient means tending to hold it against said stop, the control means being adapted to withdraw the magnet against the action of the said resilient means.

4. A device according to claim 3, wherein the stop is adjustable. 

1. A device for tensioning the thread on a textile machine, which comprises a retaining pulley rotatable by a pulled thread, and a brake for braking rotation of the pulley to give a preliminary tension to the thread downstream of the pulley, the brake comprising control means adapted automatically to modify the opposing force exerted on the pulley for modifying the preliminary tension of the thread during specific stages of the process of working the thread on the machine, the control means are adapted to render the brake instantaneously inoperative, so that the retaining pulley is the loose on its shaft, an electrical induction brake formed by a magnet and a plate which are rotatable relatively to one another on rotation of the retaining pulley, the control means being adapted to move the magnet and the plate apart from one another in order to reduce the opposing force.
 2. A device according to claim 1, wherein the plate is rigidly secured to the retaining pulley and the magnet disposed opposite the plate is mounted movably on a support.
 3. A device according to claim 2, wherein the support comprises a stop against which the magnet may bear in the advanced position, and resilient means tending to hold it against said stop, the control means being adapted to withdraw the magnet against the action of the said resilient means.
 4. A device according to claim 3, wherein the stop is adjustable. 